Microsoft's update shrinking reduces Windows 10 Insider betas by 65%

But smaller updates won't reach most users until the fall

windows 10 UUP

Microsoft last week repeated its assertion that future Windows 10 feature upgrades will shrink in size later this year, and supported the claim with a smattering of data.

Those running Windows 10's preview, labeled "Insider," will see the largest reductions in download size, the data showed.

Windows 10 differential downloads Microsoft

Windows 10's new update delivery system reduces the size of downloads -- in this case by 65% for an Insider refresh (in green) -- compared to a full-install "canonical" update (in blue), by sending only what has changed since the last update.

Microsoft first touted smaller upgrades in November, when it trumpeted the "Unified Update Platform" (UUP), a new update delivery technology that it rolled out to participants in the Insider program a month later.

Bill Karagounis, director of program management, returned to the UUP topic Thursday in a post to a company blog. "One of the biggest benefits UUP brings to our customers is a reduction in download size of build updates on PCs," Karagounis wrote.

Rather than deliver every file necessary to assemble the upgrade prior to installation, UUP sends only what has changed since the last update or upgrade. The resulting package then uses files already on the local system -- copying those that were unchanged, building new files containing the changed code just downloaded -- to generate the installation.

Such change-only updates are often called "delta" or "differential" updates, and by nature are smaller than "full" upgrade packages, which include all files, not just those that have changed since the previous refresh.

Other operating system makers already provide delta updates: Apple, for instance, offers differential updates for the macOS "point" releases during an edition's year-long lifecycle.

But until December, when Microsoft added UUP to the Insider releases, all updates and feature upgrades -- the former delivered every week or two, the latter once or twice yearly -- were full install packages that weighed in between 3GB and 4GB. With UUP in place, the size of a February 1 Insider update dropped to a median of just 910MB, 65% smaller than a February 8 full update, which Microsoft referred to as a "canonical" update, which tipped the download scale at a median of 2.56GB.

Non-Insider users of Windows 10 won't see reductions that substantial, Karagounis said, again asserting that feature upgrades should shrink by about 35% under UUP's differential regime. Microsoft did not provide data to support that claim, however.

The difference between Karagounis' 35% contention and the 65% reduction illustrated by his post's accompanying chart stemmed from the fact that with less time between updates, as with the rapid Insider tempo, differences between before-and-after files are fewer, and thus the resulting download is smaller. Rather than differences measured in weeks, as between Insider releases, feature updates are separated by months.

Because UUP will be included in the upcoming "Creators Update," the Windows 10 feature upgrade expected to ship this month or next, non-Insider customers won't see a download size savings until the next feature upgrade. That will probably appear in the fall.

Smaller upgrade downloads will mean shorter retrieval times, and for those on metered connections, less of an impact on that month's allowance. But they will not reduce the amount of time the device is occupied with installing the upgrade, a sore spot with some users. Microsoft has announced other changes for the Creators Update to address some of those update and upgrade complaints.

The much smaller build-to-build delta updates of the Insider program may be a bigger boon to Microsoft. The company has pinned much of its testing on the Insider users, making it imperative that it attracts, then retains, the largest number of testers possible. Anything it does to make the program more convenient for members, or to address complaints, would be to its benefit.

Microsoft has hinted that it wants to boost the number of testers or change the composition of the pool. Last month, for example, Microsoft announced it would add features and tools to the Insider program that would target enterprise customers.

Copyright © 2017 IDG Communications, Inc.

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